25.04.2011 Microelectronics Circuit Analysis and Design Donald A. Neamen Chapter 7 Frequency Response Neamen Microelectronics, 4e McGraw-Hill Chapter 7-1 In this chapter, we will: Discuss the general frequency response characteristics of amplifiers. Derive the system transfer functions Develop the Bode diagrams of the magnitude and phase of the transfer functions. Analyze the frequency response of transistor circuits with capacitors. Determine the Miller effect and Miller capacitance capacitance. Determine the high-frequency response of basic transistor circuit configurations. Neamen Microelectronics, 4e McGraw-Hill Chapter 7-2 1 25.04.2011 Amplifier Gain Versus Frequency Neamen Microelectronics, 4e McGraw-Hill Chapter 7-3 Transfer Functions of the Complex Frequency Name of Function Expression p Voltage Transfer Function T(s) = Vo(s)/Vi(s) Current Transfer Function Io(s)/Ii(s) Transresistance Function Vo(s)/Ii(s) Transconductance Function Io(s)/Vi(s) Neamen Microelectronics, 4e McGraw-Hill Chapter 7-4 2 25.04.2011 Series Coupling Capacitor Circuit s ) 1 s ( RS RP )C S T ( s) K 2 ( Neamen Microelectronics, 4e McGraw-Hill Chapter 7-5 Parallel Load Capacitor Circuit 1 ) 1 s ( RS RP )C P T ( s ) K1 ( Neamen Microelectronics, 4e McGraw-Hill Chapter 7-6 3 25.04.2011 Bode Plot of Voltage Transfer Function Magnitude: Series Coupling Capacitor Circuit Neamen Microelectronics, 4e McGraw-Hill Chapter 7-7 Relationship Between Rectangular and Polar Coordinates Neamen Microelectronics, 4e McGraw-Hill Chapter 7-8 4 25.04.2011 Bode Plot of Voltage Transfer Function Phase: Series Coupling Capacitor Circuit Neamen Microelectronics, 4e McGraw-Hill Chapter 7-9 Bode Plot of Voltage Transfer Function Magnitude: Parallel Load Capacitor Circuit Neamen Microelectronics, 4e McGraw-Hill Chapter 7-10 5 25.04.2011 Bode Plot of Voltage Transfer Function Phase: Parallel Load Capacitor Circuit Neamen Microelectronics, 4e McGraw-Hill Chapter 7-11 Circuit with Series Coupling and Parallel Load Capacitor S ( RS RP )C S P ( RS RP )C P fL fH Neamen Microelectronics, 4e McGraw-Hill 1 2 S 1 2 P Chapter 7-12 6 25.04.2011 Bode Plot of Magnitude of Voltage Transfer Function: Series Coupling and Parallel Load Capacitor Neamen Microelectronics, 4e McGraw-Hill Chapter 7-13 Steady-State Output Response Coupling Capacitor Neamen Microelectronics, 4e McGraw-Hill Load Capacitor Chapter 7-14 7 25.04.2011 Common Emitter with Coupling Capacitor fL Neamen 1 2 ( RSi Ri )CC Microelectronics, 4e McGraw-Hill Chapter 7-15 Common Source with Output Coupling Capacitor fL Neamen Microelectronics, 4e McGraw-Hill 1 2 ( RD RC )CC Chapter 7-16 8 25.04.2011 Emitter Follower with Output Coupling Capacitor fL Neamen Microelectronics, 4e McGraw-Hill 1 2 ( Ro RL )CC 2 Chapter 7-17 Problem-Solving Technique: Bode Plot of Gain Magnitude 1 Determine whether capacitor is producing a 1. low-pass or high-pass circuit. a. Sketch general shape of Bode plot 2. Corner frequency is f = 1/(2) where = ReqC a. Req is resistance seen by capacitor 3. Maximum gain magnitude is midband gain. a. Coupling and bypass capacitors act as shorts b. Load capacitors act as opens Neamen Microelectronics, 4e McGraw-Hill Chapter 7-18 9 25.04.2011 Common Source with Load Capacitor fH Neamen Microelectronics, 4e McGraw-Hill 1 2 ( Ro RL )CL Chapter 7-19 Coupling and Parallel Load Capacitors Neamen Microelectronics, 4e McGraw-Hill Chapter 7-20 10 25.04.2011 Small-Signal Equivalent Circuit: Coupling and Parallel Load Capacitor fL 1 2 [ RS ( R1 R2 Ri )]CC Neamen Microelectronics, 4e McGraw-Hill fH 1 2 ( RC RL )C P Chapter 7-21 Emitter Bypass Capacitor Neamen Microelectronics, 4e McGraw-Hill Chapter 7-22 11 25.04.2011 Bode Plot of Voltage Gain Magnitude: Emitter Bypass Capacitor Neamen Microelectronics, 4e McGraw-Hill A v 0 g m r RC RS r (1 ) RE A v g m r RC RS r Chapter 7-23 Two Coupling Capacitors and a Emitter Bypass Capacitor Neamen Microelectronics, 4e McGraw-Hill Chapter 7-24 12 25.04.2011 PSpice Results for Two Coupling Capacitors and a Emitter Bypass Capacitor Neamen Microelectronics, 4e McGraw-Hill Chapter 7-25 Expanded Hybrid Equivalent Circuit Neamen Microelectronics, 4e McGraw-Hill Chapter 7-26 13 25.04.2011 Short-Circuit Current Gain: Analysis of Frequency Response of BJT Neamen Microelectronics, 4e McGraw-Hill Chapter 7-27 Bode Plot: Short-Circuit Current Gain f Neamen 1 2 r (C C ) Microelectronics, 4e McGraw-Hill fT o f Chapter 7-28 14 25.04.2011 2-Port Equivalent Circuit of CBJT Thevenin Equivalent Neamen Norton Equivalent Microelectronics, 4e McGraw-Hill Chapter 7-29 Small-Signal Equivalent Circuit with Miller Capacitance: BJT CM C [1 g m ( RC RL )] Neamen Microelectronics, 4e McGraw-Hill Chapter 7-30 15 25.04.2011 Inherent Resistances and Capacitances in n-Channel MOSFET 1 C gs C gd WLC ox 2 Neamen Microelectronics, 4e McGraw-Hill Chapter 7-31 Equivalent Circuit for n-Channel Common Source MOSFET Neamen Microelectronics, 4e McGraw-Hill Chapter 7-32 16 25.04.2011 Unity-Gain Bandwidth fT Neamen gm 2 (C gs C gd ) Microelectronics, 4e McGraw-Hill Chapter 7-33 Small-Signal Equivalent Circuit with Miller Capacitance: MOSFET C M C gd [1 g m RL ] Neamen Microelectronics, 4e McGraw-Hill Chapter 7-34 17 25.04.2011 Common-Emitter Amplifier Neamen Microelectronics, 4e McGraw-Hill Chapter 7-35 High-Frequency Equivalent Circuit: Common Emitter fH Neamen 1 2 [r RB RS ](C C ) Microelectronics, 4e McGraw-Hill Chapter 7-36 18 25.04.2011 PSpice Results for Common Emitter Neamen Microelectronics, 4e McGraw-Hill Chapter 7-37 Common-Base Amplifier Neamen Microelectronics, 4e McGraw-Hill Chapter 7-38 19 25.04.2011 High-Frequency Equivalent Circuit: Common Base f H 1 f H r 2 [ RB RS ]C 1 Neamen Microelectronics, 4e McGraw-Hill 1 2 ( RC RL )C Chapter 7-39 PSpice Results for Common Emitter Neamen Microelectronics, 4e McGraw-Hill Chapter 7-40 20 25.04.2011 Cascode Circuit Neamen Microelectronics, 4e McGraw-Hill Chapter 7-41 High-Frequency Equivalent Circuit: Cascode f H 1 2 [ RS RB1 r 1 ](C 1 C M 1 ) Neamen Microelectronics, 4e McGraw-Hill f H 1 2 ( RC RL )C 2 Chapter 7-42 21 25.04.2011 PSpice Results for Cascode Neamen Microelectronics, 4e McGraw-Hill Chapter 7-43 Emitter-Follower Circuit Neamen Microelectronics, 4e McGraw-Hill Chapter 7-44 22 25.04.2011 High-Frequency Equivalent Circuit: Emitter Follower fH 1 2 [ RS RB (1 g m RL' )r ](C Neamen C ) 1 g m RL' Microelectronics, 4e McGraw-Hill Chapter 7-45 PSpice Results for Emitter Follower Neamen Microelectronics, 4e McGraw-Hill Chapter 7-46 23